Method of making brake shoes



' Oct. 20, 1925. 1,557,670

M. R. DE FRANCE METHOD OF MAKING BRAKE SHOES Original Filed NOV. 10.1924 IN VE NTOR M u'rreII RJDE TTCLTICQ" 13., 4% WW his a-horrleyPatented Oct. 20, 1925.

*PATENT OFFICE- MURRELL R. DE FRANCE, OF BELLEV'UE, PENNSYLVANIA.

METHOD or MAKING- BRAKE snons.

Original application filed November 10, 1924, Serial No. 748,863.Divided and this application filed April 18, 1925. Serial No. 24,070.

To all whom it may concern Be it known that I, MURRELL R. DE FRANCE, acitizen of the United States, residing at Bellevue, in the county ofAllegheny and State of Pennsylvania, have invented a new and usefulImprovement in a I Method of Making Brake Shoes, of which the followingis a specification.

This invention relates to a method of making a pressed metal andcomposition brake shoe for use on railway cars and similar ,vehicles,and to a method of making" a filling block constituting an element ofsuch brake shoe; this application constituting a division of applicationSerial No. 748,863,

' filed November 10, 1924.

' For a long time previous to the present invention a wide variety ofsubstances have been utilized in filling compositions for brake shoes.Among such substances may be noted fibrous asbestos, coke, cement, ironborings, iron ore, plaster, plumbago, rosin,

' sand, sawdust, wood, and other vegetable fibers. Various oxidizingvegetable oils and various gums have been used as a binder for these dryingredients. When plaster or cement has been used as an ingredient ofthe composition, water has been added to set and harden the compositionas a whole.

Brake shoes of the general type mentioned, that is brake shoescomprising a shell of pressed metal and a filling of a compositionformed of various ingredients, present certain advantages -over the castmetal brake shoes commonly in use. Such advantages reside chiefly inmanufacturing economy, which is so great that compositibn brake shoeswould largely displace cast metalshoes if the former performed under allconditions of use in as satisfactory a manner as the cast shoe.

It'may be stated in connection with cast iron shoes, that the wear onthe face of a cast iron brake shoe is by granulation. Under givenpressure and load the friction produced by this shoe on a wheelincreases inproportion to the squareof piessure until the temperature ofthe shoe is that of a dull red heat, at-which point the friction de- 0creases indirect proportion to the further heat generated. It isl'to beunderstood, of course, that under anexcessive pressure such as isproduced by a stuck brake, a cast metal shoe, or any other brake shoe,would be burned up.

The wearing away of a composition brake shoe is by pulverization ascontrasted with granulation. The wear. of the composition shoe being bypulverization, the shoe and wheel in time become so highly polished thatthe contact between the two is almost perfect. When this condition isproduced, an excessive friction greater than that specified for thepurpose for which the shoe is used is developed. It will be understoodthat this perfect contact and excessive friction is a condition which isnot possible with a brake shoe which wears away by granulation.

It should be understood, also, that the compositions which constitutethe filling material for pressed shell and composition brake shoes, arevery poor conductors of heat. This fact avoids limitation of thefriction developed by the shoe, as is the case when a cast metal shoereaches a red heat.

Previous failure of composition brake shoes to compete successfully withcast metal shoes may be traced to three defects, which had to beovercome in order to render them satisfactory under all conditions ofuse as the cast shoe. The first problem was to provide a suitable shell,which would not injure the tread of the wheel to which the brake wasapplied. This defect has been gradually eliminated by experiment andinvention. The second problem was the development of a fillingcomposition which would carry the crushing load of brakinga wheel,independently of the shell in which the composition is carried. Thisproblem is inherently connected with the first, as its solution wasnecessary in order to secure a. shell which would not injure the treadof'a wheel. It has also been successfully solved. The third problem hasbeen the development of a composition filling which would conform to thespecifications requisite friction and life, and whiclrwould also aproximate the functioning of a cast metal s cc under all conditions ofservice of railroads for and at all times during the life of the shoe.

It is this latter problem which has'hitherto remained unsolved, andwhich at the pres ent time limits the use of composition brake shoes.The disadvantages which must be overcome are those of a wearing by pul-=verization to result in perfect contact between the brake shoe and wheelwith a resultant development of friction in excess of that specified.For this reason the use of composition brake shoes has been limited tofreight cars only. For if a composition shoe be placed on passengercars, it will be found that the heat generated by excessive frictionwill be beyond the factor of safety in the operation of trains, and thatserious injury to the treads of the wheels on such trains will beproduced.

The manufacturers of composition brake shoes have been aware of thisdefect, and its disastrous consequences in the use of the -brake shoesfor years, but attempts to remedy this defect have hitherto beenineflective or impractical. Durin'g experimental work it was found thatthe various filling compositions would not develop uniform frictionthroughout the life of the brake shoe. Thus if the brake shoe wascapable of giving the specified requisite friction upon its firstapplication; by the time the shoe was partially worn away, and the shoeand the tread of the wheel to which it was applied had become thoroughlypolished, the friction was far beyond the proper specifications. Inconducting such work the inventor herein has made and tested compositionbrake shoes in which the coeflicient of friction increased as greatly asthirty per cent during the life of the shoe. Compositions in which thecoeflicient friction did not increase with use of the shoe varied froman insuflicient initial friction to substantially no effective initialfriction whatever.

The general object of the invention is, therefore,.to provide a methodof making a composition filler of such nature that it may be used in apressed metal shell to form a composition brake shoe capable ofapproximating the effect of a. cast metal brake shoe under allconditions of use, and throu'ghout the entire life of the shoe.

One specific object of the invention is to provide a method ofcompacting in a single integral block of filling composition areas orstrata of different grades of composition, which have differentcoefiicients of friction.

Another ob'ect of the invention is to provide a meth of compacting in asingle integral block of filling composition areas or strata ofdifferent grades of composition, which wear away at different ratesduring the useful life of the brake shoe.

In the accompanying drawings Figure 1 is a vertical sectional viewthrough a mold and brake shoeshell, illustrating one step in making abrake shoe by compacting a composition filler into the shell accordingto the present invention; Figure 2 is a cross sectional view on the line2-2 of Figure 1;

Figure 3 is a view similar to Figure 1, but

according to the present method, and in the manner illustrated inFigures 1, 2, and 3; Figure 5 is a cross sectional view on the line 5-5Figure 4; Figure 6 is a bottom plan view of a completed brake shoehaving a modified arrangement of the various areas of the diflferentgrades of filling composition; Figure 7 is a cross sectional view on theline 77 Figure 6; and Figure 8 is a fragmentary vertical sectional viewillustrating a manner of conducting the method of the present inventionto produce an effect in the completed brake shoe generall similar tothat illustrated inFigures 6 an 7.

In conducting the process of the present invention, as illustrated inFigures 1, 2, and 3 of the drawin s, a brake shoe shell 1 of pressedmetal is aid in a mold 2 in the position shown. Thin partition members3, which may be composed of tin or other suitable material, are theninserted, as shown, so that they extend downwardly to the interiorsurface of the back of the shell and extend upwardly almost to the topof the mold. Filling composition in a plastic and readily compressiblecondition is then introduced into the compartments 4c formed in thebrake shoe shell and mold by the partitions 3. In pursuance'of thepresent invention, the filling composition'used comprises two or moredifferent grades. show composition of two different grades used to formthe filling block of the shell, the different grades of compositionbeing introduced into alternate compartments 1 throughout the length oft'he shell.

A suitable instrument is then introduced into each of the compartments4, and both grades -of filling composition-5 and 6 are pressed down intothe position shown by dotted lines in Figure 3 of the drawings, tocompact the composition. This operation may be performed by hand.

The final pressing operation is then performed under. a relatively highpressure, and results in the formation of a single integral block offilling composition 7, which has.along its working face 8 and extendingvertically of the brake shoe shell alternate areas 9 and 10 formed bythe different grades 5 and 6 of the filling composition. The brake shoeis then in condition for baking to effect the final hardening of thecomposition filling block 7 It should be noted that the brake shoe ascompleted does not comprise a plurality of separate blocks, which mustbe interlocked or otherwise mutually secured to each other or; held inposition by a resilient pressure of The drawings i then identical withsuch the brake shoe shell. The block is, as stated, a single integralblock, but consists of vertical stratifications or areas providing areasof composition with different characteristics.

Instead of the vertically stratified areas of varying forms ofcomposition, areas of one or more varying grades of composition may beintroduced in a filling block having a surrounding area of uniformcompositionfiThis arrangement is shown-in Figures 6, 7, and 8 of thedrawings. In this modified arrangement the brake shoe shell 1 isprovided with a filling block 11, which comprises areas 12 of one gradeof composition and a' surrounding area 13 of a dissimilar grade. Theareas 12 and 13 both extend vertically the entire depth of the brakeshoe shell, as is shown in Figure 8. In order to form a brake shoehaving a filling block so arranged, it is only necessary to vary thearrangement shown in Figures 1 to 4 by introducing into the mold andshell partition members, which have closed sides, instead of the simplesingle wall partition as shown in the drawings. In such case one gradeof composition in a plastic condition may be introduced outside theclosed partition members or tubes, and one or more varying grades,likewise in plastic condition, introduced into the tubes. The operationof a preliminary pressing to compact the material, and the finalpressing operation, are steps as described above.

It will be understood that in this modified form of brake shoe thesecondary composition may be introduced by means of tubular members ofany desired form to provide areas of any desired shape in the finalfiller.

As has been previously stated, at least two formulae should be employedin providing the'composition of the different areas of the fillingblock. of the invention, these formulae must be such that differentareas having at least two different coefficients of friction areprovided on the working face of the filling block not only initially butduring the entire life of the brake shoe, as the block is worn away inuse. It is also highlydesirable that the ma- .terial in one set of areasshould tend to be worn away more rapidly than the material in the otherset of areas. This is effected in practice by having one or moreareas orsets or areas comprise material which tends to pulverization with greatrapidity. This effect causes the working face of the block to beconstantly covered with loose material,

thus preventing perfect contact between the wheeland the area or areaswhich are less susceptible to disintegration. It is also desirable thata certain ingredient, or certain ingredients, of such area or areas besuch as to cause the loose material to be as coarse as possible, thusapproximating the effect of a a change in In order to effect the objectscast metal brake shoe during its wear by granulation.

Desirable formulae for the difierentgrades of composition are given incopendingapplication Serial No. 748,863, filed November 10, 1924, ofwhich the present is a divisional application. In conducting the methodthe various areas of plastic composition, which are to be compacted intoa sing e intergal block, may comprise compositions as disclosed in theseformulae, or any other composition which will produce satisfactoryresults in use. It is of course a prerequisite that the composition becompressible while in a plastic condition and that it may be hardened,by exposure to air or by baking, into the desiredintegral block.

It should also be understood that the method of the presen inventionproduces no novel advantage in the completed brake shoe, unless theintegral filling block produced is composed of two or more grades ofcomposition which have different characteristics. The final block shouldthus oomprise two or more grades of composition which vary either intheir coefficients of friction, or in their rate of disintegration, orin their inherent tendency to become pulverized in use, or in any two orall of these characteristics. It is to be noted that while the processshows the method as conducted with only two grades of composition, no

the conduct of the method is necessary in order to incorporate three ormore different grades in a single filling block.

It should be further understood that composition filling blocks forpressed metal shells may be made by pressing the bodies of differentgrades of composition in a mold apart from the shell. This block may bethen separately baked, and the metal shell folded and pressed around theintegral block of filling composition.

What I claim is:

1. The method of making a-eomposition brake shoe which consists inpositioning a ressed metal shell within a mold-dividing the shell withinthe shell and mold by temporary partitions, inserting into differentcompartments formed by such partitions various grades of fillingcomposition in a plastic condition, withdrawing such partitions, andpressing the body of composition to compact the same into a singleintegral block.

2. The method of making a composition brake shoe which consists inpositioning a pressed metal shell within a mold, dividing the spacewithin the shell and mold by means of temporary partitions, insertinginto different compartments formed by such partitions various grades offilling composition in a plastic condition, pressing the compositionlightly within the compartments to compact it initially, withdrawing thepartitions, and subjecting the body of the composition to relativelyhigh pressure to compact the same into a single integral block.

3. The method of making a composition brake shoe which consists inpositioning a pressed metal shell within a mold, inserting into theshell and mold a plurality of grades of filling composition while inplastic condition in such manner that the several grades form separateareas therein, and pressing the body of the composition to compact thesame into a single integral block.

4. The method of making a composition brake shoe which consists inpositioning a pressed metal shell within a mold, insertlng into theshell and mold a plurality of grades of filling composition while in aplastic condition in such manner that the several grades form separatestrata therein, and pressing the body of the composition to compact thesame into a single integral block.

5. The method of making a. composition brake shoe which consists inpositioning a pressed metal shell within a mold, introducing into theshell and mold a plurality of grades of filling composition while in aplastic condition in such manner that the several grades form separatevertical strata therein, and pressing the body of composition to compactthe same into a single integral block.

"6. The method of making a com osition filling block for use in thepress metal shell of a composition brake shoe which consists inintroducing into a mold a plurality of grades of filling compositionwhile in a plastic condition in such manner that the several grades formseparate strata therein,

and pressing the body of composition to compact the same into a singleintegral bloc 7. The method of making a composition filling block foruse in the pressed metal shell of a composition brake shoe whichconsists in introducing into a mold a plurality of grades of filling comosition while in a plastic condition in sue mannerthat the severalgrades form separate Vertical strata therein, and pressing the body ofcomposition to compact the same into a single integral block.

8. The method of making a composition filling block for use in thepressed metal shell of a composition brake shoe which consists inintroducing into a mold a plurality of grades of filling compositionwhile in a plastic condition in such manner that the several grades formseparate areas therein, and pressing the body of composition to compactthe same into a single integral block.

9. The method of making a composition filling block for use in thepressed metal shell of a composition brake shoe which consists individing the space within a mold by means of removable partitions,inserting into different compartments formed by such partitions variousg'lrades of filling composition, and pressing t e body of com osition tocom act the same into a singl bloc 7 10.. The method of making acomposition filling block for use in the pressed metal shell of acomposition brake shoe which consists in dividing the space within amold by means of removable partitions, inserting into e integraldiflerent compartments formed by such partitions various grades offilling composition, subjecting the composition to a slight initialpressure to initially compact the same, and subjectin the body ofcomposition to a relatively hig pressure to compact the same into asingle integral block.

b I15 witness whereof, I hereunto set my MURRELL R. DE FRANCE.

